Rik,
1. "Where is the alpha coming from? Is it already in the image that you're
applying blending to?"
I created the images A and B in Photoshop, A has opacity
75% and B has 100%, so the alpha is coming
from the images yes.
2. "If so, you need to alpha blend with the background first and then
blend."
You mean alpha blend the top image A with bottom/background image B?
And then blend with...? I am confused, so I am not supposed to use that
formula?
Thanks